There are thousands of digital printers sold each year by many different manufacturers. Digital printing technology has been widely used for several decades. Typically, digital printers are used to print on standard thickness paper, commonly known as “copy paper” of common sizes such as 8.5″×11″ or A4. Since the majority of usage on these printers consists of this type of paper, the feed systems on these printers are designed to handle this specific material well. A stack of paper is placed in a hopper that is incorporated into the body of the printer. The printer takes one sheet of paper at a time by pulling the top sheet off a stack of paper in the hopper with a feed roller or “feed tire” that is resting on the top of the stack.
Although this method works very well on standard paper, it is not capable of feeding difficult or thick sheets, such as envelopes, postcards, folded pieces, and other thick materials. The term “sheet” is used herein to encompass not only single sheets of paper, but also such things as envelopes, postcards, CDs, credit cards, labels, calendars, or any other object, generally on the order of a few thousandths of an inch to about ⅜ of an inch thick, and sufficiently flexible to flex on the order of 1/16 to ⅛ inch, that can be fed from a stack and that can be printed by the printer into which it is fed.
To accommodate occasional feeding of these thick or difficult sheets, many digital printers include a “manual feed tray” or “multi-purpose feed tray” or “bypass tray” that is open to the exterior of the digital printer when in use and is most often hinged to one side of the printer. In this tray (hereinafter called a “manual feed tray”), the user can normally place a few envelopes, cards or other thick sheets for printing when not printing on standard paper. Although these manual feed trays work reasonably well, they have very small limits on the size of the stack of sheets, and therefore cannot be used for large volumes of printing without constant re-loading of media. In addition, these manual feed trays also incorporate a top feed design, meaning that they have a feed roller that pulls the top document off the stack in the manual feed tray. This means that the operator cannot load documents into the feed tray until the prior stack is depleted.
Attempts have been made to solve this problem by providing a separate sheet feeder that feeds envelopes to the feed roller of the manual feed tray. However, they require that changes be made to the printer's manual feed tray to accommodate the feeder. The manual feed trays of most existing digital printers are attached to one end of the digital printer, and typically are hinged to the printer. The manual feed tray typically rests at a slight angle, rising upwards as it extends away from the hinged point. The manual feed tray also incorporates media guides and other components that are positioned near the feed roller area. For these reasons, the manual feed tray blocks access to the feed roller and feed area on the printer. The manual feed tray therefore must be removed from the printer when using prior art add-on feeders. This eliminates the ability to use the manual feed tray without the use of the add-on feeder or for its normal purposes completely, unless the manual feed tray is re-attached to the printer.